The selection of compatible materials depends strongly on the process environment. As described in the first section of this chapter, most of the materials used for the pyroprocess are in moderate corrosion condi­tions during normal operation. Carbon steels and stainless steels can be used without corrosion problems. For example, long-term durability of steel materials has been tested with LiCl-KCl salt and liquid Cd with actinides and FP at approximately 500 °C. On the other hand, stainless- steels are not suitable for the crucible containing liquid Cd because nickel dissolves in them. No detectable damage has been reported for a mild steel crucible in a laboratory-scale electrorefiner (Battles, 1993) or for Mo a steel crucible in INL’s engineering-scale electrorefiner. The integrity of Mo steel was also confirmed in CRIEPI’s experiments with an electrorefiner and with a counter current contactor. The materials suitable for the more severe conditions in the pyroprocess are described in this section.